1. Cross Reference to Related Applications
This application is related to U.S. application Ser. No. 07/209,056 filed June 20, 1988, and entitled TAMPER RESISTANT SHACKLE SEAL which application is in the name of the present inventor.
2. Field of the Invention
This invention relates to seals of the type which are utilized for security and which include a housing connected to a strap member having an end which is receiving within the housing and locked therein. Such seals are utilized to prevent unauthorized openings or tampering of the seals which unauthorized tampering would not be readily detectable. More specifically, the present is directed to such a seal which is formed utilizing an assembly of locking teeth which are slidingly received within the housing and which are formed of a material having a higher melting point than the housing and the strap.
3. Description of the Related Art
Shackle seals have become well developed over the years. They are used for security sealing the doors associated with cargo containers and cargo trucks and the like. Among the requirements for such seals is that they are easy to use, that they function to reflect whether or not there has been unauthorized tampering of the seals during shipment of the cargo and that they are inexpensive. In view of the foregoing, one piece plastic seals have become the shackle seals of choice in most instances. Such seals are easy to stock, non-corrodible, easy to place in service, and easy for the authorized person to break and dispose of at the appropriate time.
Since truck and container cargos are valuable and subject to pilferage, the seals utilized therewith must be strong enough to withstand ordinary handling and therefore must not be subject to inadvertent breakage. Of special importance is that the structure of the seals be such that they may not be tampered with, opened and reclosed, without evidence of such opening being apparent.
The use of shackle seals which incorporate plastic housings having internal spring-like fingers which are provided to engage the end portion of a shackle or strap which is integrally formed with the housing is well known. In order for such housings to be secure against tampering, it is necessary that both ends of the housing be closed to prevent the insertion of pointed instruments which may be utilized to manipulate the spring-like fingers thereby allowing the withdrawal of the end portion of the strap or shackle and allowing access to a container by effectively defeating the locking engagement of the seal. Due to the internal structure of such seal housings, it is not economically feasible to manufacture such housings with one of the ends being molded closed.
In an effort to overcome the disadvantages of most prior art structures, in applicant's co-pending U.S. application Ser. No. 07/209,056 filed June 20, 1988, a special plug is disclosed for effectively sealing or closing one end of the housing after the pointed end of the strap has been inserted through the opposing end of the housing. More specifically, the seal includes a housing having opposite ends and which includes a plurality of spring-like fingers which are integrally molded within the housing and which are utilized to engage a reduced neck portion adjacent the pointed enlarged head portion of the integral shackle or strap of the seal. Thereafter, the opposing end of the housing is closed utilizing the separate plug. The plug includes an annular recess therein which is frictionally engaged by an annular rib formed internally of the housing. The spacing of the rib is such that the end portion of the plug is flush with the end of the housing. Due to the relationship between the rib and the recess of the plug, it becomes impossible to insert an instrument between the plug and the housing in order to obtain access to the locking fingers within the housing without providing an obvious visual indication of seal tampering.
Unfortunately, it has been noted that in rare instances it may be possible to apply heat to the seal, especially when the seal is formed of material such as polyethylene or polypropylene. The heat generated by a conventional electric hair dryer may be sufficient to soften the housing thereby making the components susceptible to opening and permitting surreptitious entry or unlocking of the seal. A further problem inherent in the manufacture of prior art seals, such as disclosed in applicant's co-pending application referenced above, is the cost of molding which is increased by the rate of production which must be slowed in order to permit the mass of plastic that must be molded to provide the spring elements inside the housing to be pushed through the mold and cooled.
Other prior art attempts to provide a closure for the open end of housings in shackle type seals are disclosed in U.S. Pat. Nos. 4,059,300 to Moberg et al., and 3,466,077, Moberg. In these patents, the closure for the open end of the housing is provided by an added step of molding over an end portion following the initial molding of the housing.
In U.S. Pat. No. 3,954,295 to Harley a plug element is disclosed for closing one end of the housing which plug is retained on a tab integrally formed with the housing. In U.S. Pat. No. 4,229,031 a plug is provided for closing one end of the housing which incorporates a pair of legs which compress inwardly when the plug is inserted into the housing. In U.S. Pat. No. 4,319,776 to Moberg a similar plug arrangement is disclosed.
Another example of a cap member for a plug is disclosed in U.S. Pat. No. 4,609,218 to Chevillard et al. In applicant's prior U.S. Pat. No. 3,712,655 a shackle seal is disclosed which incorporates indentations in a strap to provide an appropriate ease of shackle breakage to indicate tampering of a shackle seal. The above referenced patent to Harley also discloses the use of an opening in a strap member for facilitating breakage of the strap in order to indicate tampering with the seal.
U.S. Pat. No. 4,559,676 discloses a shackle seal having a tip member which has a portion that is compressed when it is inserted within the housing.
None of the aforementioned prior art shackle seals disclose the need for forming the locking components of a shackle type seal of a material having a higher melting point than the housing and strap or shackle of the seal in order to thwart unauthorized tampering of such seals.